Conventionally, in an electrophotographic image forming apparatus, a long lifetime and stability of image quality are required. The lifetime of a photoreceptor that is an important functional member in an image forming apparatus is determined by the degree of abrasion of the photosensitive layer. Also, image quality degradation is caused by the generation of small flaw and abrasion unevenness, an image forming unit including a photoreceptor needs to be replaced.
Recently, a protective layer by a crosslinked cured resin is laminated on the surface of the photoreceptor, thereby improving abrasion resistance, scratch resistance and environmental stability, and prolonging the lifetime.
In addition, recently, as a charging system of a photoreceptor, a roller charging system that is advantageous for better picture and smaller device and can reduce the amount of generation of oxidized gas such as ozone and NOx, as compared to a scorotron/corotron charging system, is adopted. Here, the roller charging system refers to a charging system that charges a photoreceptor by bringing a charging member comprising a charging roller into contact with or closer to the surface of the photoreceptor.
However, the problem is that, when charging is performed by roller charging system, the surface of the photoreceptor is degraded, and the resistance of the surface of the photoreceptor cannot be kept high, thus image deletion occurs in a high-temperature and high-humidity environment.
In addition, the problem is that, when the photoreceptor having a protective layer by a crosslinked cured resin is charged by roller charging system, the rate of degradation on the surface of the photoreceptor is higher than the rate of surface polishing, and the torque is increased by the adhered discharge product, and cleaning failure accompanying warpage or chipping off of a cleaning blade or the like or toner filming is caused.
In order to solve the problems of cleaning failure and toner filming, a method of applying lubricant to the surface of the photoreceptor to form a film of the lubricant on the surface of the photoreceptor and reduce adhesion of the toner is known. This allows the torque of a cleaning blade to be reduced, and cleanability to be improved.
However, in the roller charging system, the problem is that, when charging is repeated, the lubricant is degraded to change into a water-absorbing material, thereby further promoting image deletion in a high-temperature and high-humidity environment.
In order to solve the problem of image deletion by the degraded lubricant, it is necessary to remove the degraded lubricant and then constantly supply new lubricant.
JP-A-2008-122869 describes an image forming apparatus in which a lubricant supplying part is disposed on the upstream side of a cleaning part in the rotation direction of the photoreceptor, and a lubricant removing part that removes powder lubricant by a non-contact electrostatic roller is disposed on the downstream side of a cleaning part and the upstream side of the charging part. However, in this image forming apparatus, the problem is that, the lubricant is not sufficiently laminated before charging by the charging part, thus the surface of the photoreceptor is degraded by charging by the charging part, and the resistance of the surface of the photoreceptor cannot be kept high, thus image deletion occurs in a high-temperature and high-humidity environment.